For the second time in six months union workers walked the picket line Wednesday at UC San Diego hospitals in La Jolla and Hillcrest.

The technical and service workers, represented by the American Federation of State, County and Municipal Employees, listed hospital understaffing and retaliation as their main reasons for the one-day strike which took place at university medical campuses across the state. The university insists the real reason for the work stoppage is an unwillingness by union members to comply with pension cuts.

The two sides have been in contract negotiations for 18 months, and workers staged a two-day strike on roughly the same issues in May.

Union organizer Ysenia Godinez said service workers began marching, signs in hand, before dawn. She said about 240 workers from Thornton Hospital in La Jolla were marching along with about 600 at UC San Diego Medical Center in Hillcrest. Additional maintenance workers from the university’s main campus, who are also members of the union, were part of those counts.

By 10 a.m. workers were marching from a meet-up point on Voigt Drive back to the front entrance of Thorton, chanting, banging on pots and pans and waving signs under the watchful eyes of police officers and campus security.

Marisol Bermea, who said she is a check-in coordinator at Moores Cancer Center, walked with her fellow service workers Wednesday. Like others, she cited understaffing as the main reason why she walked off the job. The union held a two-day strike in May, voicing the same general objections, a move that failed to push the university toward terms that workers would consider acceptable.

Bermea said the latest strike is proof that the union is not going away.

“We need to show them that we’re still out here fighting, and we are not going to give up,” Bermea said.

But choosing to picket did not come without costs to patients.

According to UC San Diego, a total of 171 medical procedures, including 100 elective surgeries, previously scheduled for Wednesday, were moved to other days because of the strike, which involves technical workers who operate equipment at the hospitals, including X-ray and ultrasound technicians.

San Diego resident Homer Rivera was one of the patients whose procedure got rescheduled for Nov. 22. Rivera said in an email that the strike put him, and all of the others whose procedures were canceled, through undue stress.

“Nobody has thought about the repercussions of what the strike is going to cause,” Rivera said.

The strike did not seem to cause any immediate medical problems at UC San Diego hospitals Wednesday.

Margarita Baggett, the health system’s chief clinical officer, said about 160 temporary workers were brought in to fill the shifts of those who left their jobs. She said many union workers came to work despite the strike.

“We’ve had no delays in pharmacy, radiology or lab. We’ve been business as usual all day long,” Baggett said at about 1 p.m.

Baggett said it will take between one and four days for the health system to catch up on the backlog of work created by the strike.